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The authors give a corrected form of the Korobov algorithm of optimal open pit determination and describe a method of optimising the mining sequence within a preliminary pit design. A method of automatically including roadways is also given.

Jan 1, 1992

By G. X. Wang, J. O. Marsden, M. C. Fuerstenau

Zinc cementation of high-temperature carbon eluates is now used extensively in gold processing to replace electrowinning. Under these conditions, zinc consumption is high. In this paper, zinc solubility is press rated us functions of temperature, cyanide concentration and pH in the presence of gold, silver and mercury cyanides (both individually and in combined solutions). Based on the experimental results, cementation of these metals is characterized and discussed. The importance of cyanide concentration in cementation efficiency and the effect of mercury and its co-precipitation onto zinc are also discussed.

Jan 1, 1997

By Glenn P. Jones

Laterization of syenite and other rocks in north Alabama produced material which was picked up and carried by streams to southeast Alabama. These streams deposited the aluminum rich material in the sinkholes of a karst topography developed on the Clayton Limestone. Measurement of the bearing of the long axis of each deposit in the Screamer area, along with plotting the location of these deposits on a map, indicate a depositional pattern controlled by local fractures or solution zones in the Clayton Limestone. The sinkholes and channels dictated the original structure of the deposits. Additional structure changes have resulted since compaction of the deposits by continued solution of the underlying limestone. The original material in these deposits was enriched by the removal of silica to form bausite and bauxitic kaolin during deposition and compaction. Subsequent ground water action has reintroduced silica into the deposit leaving a core of bauxite.

Jan 1, 1972

By Park. D. W., Y. M. Jiang, L. A. Morley, W. Keeton

Underground room-and-pillar mining operations in the Warrior Coal Field in Alabama frequently suffer instability due to soft floors and thinly-laminated immediate roofs. This investigation concerns a mine that was experiencing ground-control problems with weak floor conditions. Several roof falls occurred locally, and as much as 0.6 m (2 ft) of floor heaves have been experienced. The paper presents the results of comprehensive analyses conducted on floor heave, roof sagging, pillar- penetration and floor bearing capacity using instrumentation and numerical modeling.

Jan 1, 1993

By James P. Rider, Charles D. Taylor, Edward D. Thimons

Research was conducted to investigate how ventilation of a mining face is affected when scrubber flow is greater or less than intake flow. Tests were conducted in a full-scale surface test gallery built to simulate a mining entry with a continuous mining ma- chine at the face. Methane gas was released at constant flow at the mining face. Gas measurements taken at six locations near the face were used to evaluate how well the face was being ventilated. Increasing scrubber flow resulted in lower methane levels even when scrubber flow was much greater than intake flow.

Jan 1, 1997

By Ahmed M. Nofal

This article reviews some important characteristics of the known Egyptian phosphate deposits, such as mining conditions, transport criteria, quality of products affecting their export markets and utilisation in fertilizers industry. Special attention will be given to the newly discovered large deposit of Abu-Tartur with some billion tons of ore reserves. A big project is now under implementation on Abu-Tartur deposit where the long-wall method of underground mining will be applied and a flow sheet of beneficiation will be in operation including a particular feature nontraditional in phosphate processing: high-intensity magnetic separation to eliminate dolomite impurities. Comparison with some international phosphates will be tried in order to trace the situation of Egyptian phosphates in the world market.

Jan 1, 1993

By C. K. Nworu, L. O. Asuquo, C. O. Nebo

Selective flocculation studies of Agbaja iron ore with starch-type and nonionic polyacrylamide-type flocculants has been conducted to determine the effect of flocculant type. The results indicate that corn starch was slightly better than cassava starch in selectivity performance. Cassava starch was in turn better than Superfloc 16, while the poorest results were obtained with commercial starch. Sodium humate shows better dispersive capability, and thus enhanced flocculation results, than sodium silicate. Pulp pH affects the zeta potential, polymer chain configuration and hence selective flocculation. Overall results indicate that recovery and separation of this very fine grained iron oxide by selective flocculation is feasible.

Jan 1, 1995

By I. de Jong, G. Van Weert

Silver cyanide adsorbs extremely well on activated carbons. This suggests that the addition of soluble silver salts to trace cyanide containing waste streams should allow efficient cyanide removal with active carbon. Silver losses, however, would make this method expensive and also objectionable, since silver has biocidal effects. When silver impregnated carbon is used, these problems are overcome. Test work has shown that such silver remains on or in the active carbon, that cyanide concentrations can be reduced to the level of detection (< 5 ppb) and that the silver impregnated carbon can be reactivated with equipment similar to that now in use at gold milling operations. Initial results on the type of carbon, the impregnation procedure and the level of silver, and the effect of repeated regeneration are discussed.

Jan 1, 1992

By Ching Wu, David A. Sutter, Peter Frobenius

The MUNI Metro Turnback (MMT) Project includes a 256 m (840 ft) twin tunnel section, which connects to the Embarcadero Station, and runs under Market Street in San Francisco. The tunnels go through a mixed face condition of fill at top and Bay Mud at bottom, and a significant number of buried timber piles. This paper presents the selection of tunneling equipment, excavation methods, excavation support and chemical grouting; specification of timber pile cutting methods; and steel lining analysis and design. This paper also reports on the initial phase of the tunnel construction.

Jan 1, 1995

By H. M. Giegerich

About Cominco Only the original Broken Hill zinc deposit in Australia is larger than Cominco&apos;s Red Dog deposit. Indeed, the third largest zinc deposit in the world is Cominco&apos;s own Sullivan mine in British Columbia. The production plan at Red Dog is based on mining 1.9 Mt/a (2.1 million stpy) or ore, to produce 635 kt (700,000 st) of zinc and lead concentrates. At full production, Red Dog will be the largest zinc mine in the Western world. It will also be one of the lowest cost producers in the Western world. And Red Dog will be one of the first major hardrock mines to operate in Alaska in modern times. The Red Dog project will be the third and largest of Cominco&apos;s Arctic mining developments in the past 13 years. The company&apos;s Black Angel mine in Greenland started up in 1973. And the Polaris mine, high in the Canadian Arctic, began production in 1982. Red Dog is one of the world&apos;s great mineral deposits. It is a unique combination of large size, high grade, and a waste-to-ore ratio less than 1:1. The present mineral reserve (Table 1) is estimated to be 77 Mt (85 million st), at a grade of 17.1% zinc, 5% lead, and 82 g/t (2.4 oz per st) of silver. Mine life is estimated at nearly 50 years. Cominco is the largest producer of lead and zinc in the Western world. Cominco&apos;s smelter in southern British Columbia is the largest lead and zinc plant in the west. Cominco also produces copper, steel, tin, gold and silver, along with potash, ammonia, urea, and phosphate fertilizers. But Cominco&apos;s major products are lead and zinc. At present, Cominco produces more than 10% of the Western world&apos;s needs for these metals. Background-Red Dog The Red Dog mineral deposit is located in northwestern Alaska, about 960 km (600 miles) by air from Anchorage, Alaska&apos;s largest city. The Red Dog region is home to more than 5000 people living in 11 villages. The largest village is Kotzebue, with a population of about 2500. The village is located about 144 km (90 miles) southwest of the mine. The country around Red Dog features rolling hills, leading into mountains to the north and east. The deposit, at an elevation of 305 m (1000 ft), is in permafrost. But the area is not nearly as cold as that encountered in the Canadian Arctic, or on Alaska&apos;s North Slope. At Red Dog, the permafrost is relatively fragile. It can be thawed fairly easily, a factor in engineering designs. Red Dog Creek flows through the mineral deposit. One of the natural phenomena at Red Dog is the presence of significant heavy metal contamination in the creek. This has eliminated all fish in the vicinity of the deposit. The contamination, and resulting mineral stain, led to the discovery of Red Dog. The staining is caused by rain and snowmelt. This leaches the heavy metals from the mineral zone, which comes right to the surface in many places. As mining progresses, this surface mantle will be removed. This will

Jan 12, 1986

By Merwin Bernstein

Peru has been an important source of metals since Aug. 29, 1533. On that day Francisco Pizarro took charge of the 24 t (772,000 oz) of gold and silver that constituted Atahualpa’s ransom. At today’s prices, the value of that booty ranges between $100 and $150 million, depending on the proportion of gold to silver. Since then, Peru’s silver and gold production has been legendary. Current mine production Most of Peru’s metals are mined from the Andes Mountains and its foot-hills. The Andes run the length of the country parallel to the Pacific coastline from Ecuador to Chile, a distance of nearly 3000 km (I 875 miles). They are about 300 km (187 miles) wide and much of the range is more than 3000 m (9900 ft) in elevation. High plateaus (altiplanos) occupy a large part of the range. Both flanks are rutted by large valleys and canyons. Many of these peaks are prodigious. which make road building expensive and adds to the cost of mining.

Jan 1, 1993

By N. S. Harding, M. C. Mai, A. G. Fonseca

Many coal characteristics affect combustion performance. Mill wear, boiler efficiency and derate, slagging, fouling, and ash collection and removal are only a few of the impacts of coal quality on boiler performance. The ability to assess fuel characteristic impacts on busbar costs is essential, although difficult to obtain. The relationships between coal characteristics and ignitability, operability, slagging, and fouling were investigated. The examination of combustion data/performance from a laboratory study, a boiler simulation system (pilot combustor), and commercial boilers indicated the benefits of burning improved quality coal. The specific effects of cleaning are discussed. A validation of the necessity of commercial-scale and/or pilot-scale testing is presented.

Jan 1, 1988

By A. P. Chaves, A. Gomes

The cyanidation and adsorption processes at Fazenda Brasileiro mine were studied with the aim of increasing hydrometallurgical recovery. Technical evaluation of the processes consisted of (i) quantitative mineralogy of ore samples collected in different points of the circuit, and (ii) comparison of plant performance in the original (designed CIP) and in the modified (current CIP/CIL) circuits. An empirical correlation between process variables and gold grades in the cyanidation tailings was established. The suggested modifications in the circuit and in the operation conditions led to an increase in gold recovery, from 91 to 93.5%. Annual revenue is expected to show an increase of approximately US$ 1 million.

Jan 1, 1998

By G. F. Revey

All underground operations have limiting factors that influence overall profitability. Hoisting, hauling, available headings, labor, milling capacity and other factors limit how much material can be removed from an underground mine. Consequently, when mines use limited labor to handle the additional rock from overbreak and to perform extra ground support tasks, productive activity is replaced by nonproductive work. Mining economics are further penalized when overbreak causes dilution of ore grades. This paper reviews the organizational systems that mines have been using to create environments that foster the creation of successful overbreak-control programs. Actual case histories document the various quality-improvement techniques, worker incentives and practical project-management systems used by these mines. A brief review of controlled-blasting technology sources and overbreak-measurement tools is also included.

Jan 1, 1999

By Danqing Xu, A. W. Khair

This paper presents a laboratory simulation of regrinding and resulting dust generation. An Automated Rotary Coal Cutting Simulator (ARCCS) was modified to conduct regrinding experiment. In order to estimate the effects of coal properties and operating parameters on regrinding and dust generation, an orthogonal fractional factorial experimental design was implemented in regrinding experiment. Marple personal cascade impactors, Series 290, were used to measure dust concentration during experiment. Three types of coal seams, namely, Waynesburg, Pittsburgh, and Lower Kittanning, were used to represent different coal properties. Experimental results and complete parametric analysis were presented.

Jan 1, 1991

By O Gutsche, Fuerstenau D. W., R. Ravikumar

Six minerals and one ore, namely, barite, dolomite, galena, limestone, quartz, quartzite and taconite, were ground in single-particle comminution mode in a rigidly mounted roll mill with different levels of energy input. Grindabilities were determined from the median size of the self-preserving product size distributions, which was taken as a measure of the fineness of the ground material in an empirical energy-reduction ratio relationship. These values reflect the inherent resistance of the solids to mechanical size reduction that are least distorted by particle-particle interference effects, grinding characteristics, energy efficiency of the milling system employed and the extent of the fineness specified.

Jan 1, 1992

By Gordon R. Wicker, Peter V. Avotins, Steven S. Ahlschlager

Laterite ore slurries exhibit Bingham plastic behavior and can be characterized by the magnitude of their yield point and Bingham viscosity. These two parameters are affected by ore composition, solids concentration, and temperature and are used to predict the pressure drop in pipelines and heat transfer coefficients in shell-and-tube heat exchangers. In cycloning of laterite slurries, the calculated cut size is corrected by factors obtained from the rheological parameters.

Jan 1, 1979

By Robert E. Carver

Opaline clays from central and eastern Georgia are widely used as industrial and domestic absorbants, principally as insecticide carrier and animal litter. The clays are classified as fuller&apos;s earth, although they &e somewhat atypical of the group, since opal (cristobolite) is commonly the dominant clay-sized mineral. A preliminary investigation of absorption characteristics indicated that water vapor absorption (264 days) is&apos; related to opal content as determined by x-ray diffraction peak height ratios. Ethylene glycol vapor absorption is related to montmorillonite content. Contact absorption of water is complexly related to surface absorption, porosity, opal content and montmorillonite content, and may be as great as 112% of the original sample weight. The most absorbent clays are highly porous (to 65%) and contain both montmorillonite and opal.

Jan 1, 1972

By D. W. Horsfall

The different types of processes used in fine coal beneficiation in the Republic of South Africa are listed, together with data giving an indication of their separating efficiencies The two classes of coal, fines and ultra-fines, present in the -0,s m fraction of the run of mine coal are discussed, with special reference to their beneficiation characteristics. Using those properties, together with the data on plant efficiency, case studies are worked out to indicate the advantages and disadvantages of the different processing routes available. The paper closes with an indication of areas where research is required to enable some of the processes to be applied to a greater extent than is presently the case.

Jan 1, 1988

By A. Marabini, G. Belardi, N. Sheau, F. Veglio

The present paper deals with the modelling of a Multi-gravity separator in the treatment of chromite fines. A first screening study was carried out by 2" full-factorial experiments in order to check the main effects and interactions among the investigated factors: shake frequency, shake amplitude, tilt angle and washwater flowrate were taken in consideration in the study. Two size fractions were employed in the experimental tests. Successively, considering the factor with larger influence on the Cr203 and SiO2 grade and Cr203 recovery in the concentrate, a further improvement of the experimental design was performed to determine empirical models to describe the behaviour of the MGS in the mineral treatment. The results show how intrinsic interaction among the factors take place, highlighting that an optimization study must be carried out considering all the MGS setting parameters.

Jan 1, 1995